Details for Patent: 6,428,528

Title:	Needle assisted jet injector
Abstract:	A needle assisted jet injector and method for jet injecting medicament are disclosed. In one embodiment of the injector, the needle is retractably located within an injector nozzle assembly. Upon activation of the energy source, a portion of the needle extends past the nozzle assembly and penetrates the outer layer of skin to deliver the medicament via jet injection to a deeper region. After activation, the needle retracts back into the nozzle assembly. In another embodiment, the needle is fixed to the end of the nozzle assembly. In both embodiments, the length of the portion of the needle that penetrates the skin is less than 5 mm.
Inventor(s):	Sadowski; Peter L. (Woodbury, MN), DcBoer; David M. (Waconia, MN), Berman; Claude L. (St. Paul, MN), Lesch, Jr.; Paul R. (Lexington, MN)
Assignee:	Antares Pharma, Inc. (Minneapolis, MN)
Filing Date:	Feb 24, 1999
Application Number:	09/256,310
Claims:	1. A jet injection device comprising a housing, a retractable injection-assisting needle at a distal end of the injector, a nozzle assembly defining a fluid chamber, having an opening for slidingly receiving at least a portion of the needle and being removably associated with the housing, a plunger movable in the fluid chamber, a trigger assembly, and an energy generating source operatively associated with the trigger assembly so that movement of the trigger assembly activates the energy source to move the plunger in a first direction to expel a fluid from the fluid chamber, said retractable injection-assisting needle comprising: a needle tip located at a distal end of the needle with at least a portion configured and dimensioned to slide through the nozzle assembly opening; a discharge channel within the needle tip and terminating in an orifice through which the fluid is expelled; a body portion to direct fluid towards the discharge channel; a plunger receptor configured and dimensioned to receive at least a portion of the plunger; and a retraction element operatively associated with the needle and disposed substantially within the nozzle assembly; wherein the needle is located within the nozzle assembly in a retracted position prior to activation of the energy source; movement of the plunger in the first direction upon activation of the energy source results in (1) at least a portion of the needle tip extending beyond the nozzle assembly opening to a needle insertion point, and (2) the fluid is expelled through the needle tip and past the needle insertion point to an injection site, the retraction element returns the needle tip to the retracted position after activation of the energy source, the needle insertion point is located at the needle tip and less than about 5 mm from the nozzle assembly opening, and the injection site is substantially remote from the needle tip. 2. The injection device of claim 1, wherein the retraction element is a resilient O-ring, a spring, or a flexible membrane which moves to allow extension of the needle tip beyond the nozzle assembly opening and then returns to its original position to return the needle tip to its retracted position. 3. The injection device of claim 1, wherein the needle body has an exterior surface which includes a ridge or recess for accommodating the retraction element. 4. The injection device of claim 1, wherein a shoulder is disposed between the needle tip and the needle body for accommodating the retraction element. 5. A jet injection device comprising a housing, a retractable injection-assisting needle at a distal end of the injector, a nozzle assembly defining a fluid chamber, having an opening for slidingly receiving at least a portion of the needle and being removably associated with the housing, a plunger movable in the fluid chamber, a trigger assembly, and an energy generating source operatively associated with the trigger assembly so that movement of the trigger assembly activates the energy source to move the plunger in a first direction to expel a fluid from the fluid chamber, said retractable injection-assisting needle comprising: a needle tip located at a distal end of the needle with at least a portion configured and dimensioned to slide through the nozzle assembly opening; a discharge channel within the needle tip and terminating in an orifice through which the fluid is expelled; a body portion to direct fluid towards the discharge channel; a plunger receptor configured and dimensioned to receive at least a portion of the plunger; and a retraction element operatively associated with the needle and disposed substantially within the nozzle assembly; wherein the needle is located within the nozzle assembly in a retracted position prior to activation of the energy source; movement of the plunger in the first direction upon activation of the energy source results in at least a portion of the needle tip extending beyond the nozzle assembly opening and less than about 5 mm from the opening, the retraction element returns the needle tip to the retracted position after activation of the energy source, and the needle body has a funnel-shaped interior tapering towards the discharge channel to accelerate the fluid as it is discharged to a site that is substantially remote from the needle tip. 6. A method of delivering a medicament, comprising: puncturing the epidermis with a needle tip to create a hole of less than about 3 millimeters in depth and confined to the epidermis; and jet injecting a medicament in a single injection at a pressure of less than about 4000 p.s.i. through the needle tip and hole to a layer of tissue below the epidermis and substantially remote from the needle tip, whereby the medicament is delivered in less than one second, and wherein the needle tip is part of a retractable needle of a jet injection device.